Method for sending an acknowledgement to an ingress mesh point in a mesh network and a medium access control frame format

ABSTRACT

The present invention relates to a method for confirming the delivery of a data packet in a mesh network by sending an acknowledgement (ACK) to an ingress mesh point (IMP). A mesh network comprises a plurality of mesh points that are wirelessly linked together. A data packet sent by a station (STA) is received by an IMP. A MAC frame is generated for transmission of the data packet and the frame is forwarded to an egress mesh point (EMP) in order to provide a service by the mesh network. The MAC frame includes a field comprising an IMP address and an EMP address. When the EMP, (or optionally an intermediate mesh point), receives a data packet successfully, the EMP or the intermediate mesh point sends an ACK to the IMP or preceding mesh point.

CROSS REFERENCE TO RELATED APPLICATION

This application is a Continuation of U.S. patent application Ser. No.11/202,974 filed Aug. 12, 2005, which claims the benefit of U.S.provisional application No. 60/608,763 filed Sep. 10, 2004, the contentsof each being incorporated by reference as if fully set forth herein.

FIELD OF INVENTION

The present invention relates to wireless communication systems. Moreparticularly, the present invention relates to a method for sending anacknowledgement (ACK) to an ingress mesh point (IMP) in a mesh networkand a medium access control (MAC) frame format.

BACKGROUND

A mesh wireless local area network (WLAN) is a wireless networkcomprising two or more mesh points interconnected via wireless links.The mesh network typically serves one or more wireless stations (STAs)within the operating range of the mesh network. A mesh point is anyentity within the mesh network which contains a MAC and physical layer(PHY) interface to a wireless medium and supports WLAN mesh services. AnIMP is a mesh point through which data enters the mesh WLAN and anegress mesh point (EMP) is a mesh point through which data exits themesh WLAN. Data sent by a STA is routed from the IMP to the EMP throughthe mesh WLAN.

IEEE 802.11 standards are one of the standards defining the wirelessprotocol for a mesh WLAN. Current IEEE 802.11 standards define anacknowledged mode that allows for more reliable data delivery at thelower layers. However, the current acknowledgement mechanism does notwork in a mesh network since multiple hops are required over the meshnetwork before the data is delivered to the destination.

In a mesh WLAN, a communication between an IMP and an EMP can berequired. As shown in FIG. 2, a prior art MAC frame does not contain IMPMAC address during the multi-hop transmissions. Therefore, the EMP isunable to identify and communicate with the IMP. There is no mechanismor frame format for sending an acknowledgement between the IMP and theEMP in the mesh WLAN. This seriously limits the reliability of the datadelivery. Since there is no ACK mechanism between the IMP and the EMP,the IMP cannot know if the data through the mesh network has beencorrectly received by the EMP.

SUMMARY

The present invention relates to a method for confirming the delivery ofa data packet in a mesh network by sending an ACK to an IMP. The meshnetwork comprises a plurality of mesh points that are wirelessly linkedtogether. A data packet sent by a STA is received by an IMP. A MAC frameis generated for transmission of the data packet and the frame isforwarded to an EMP in order to provide a service by the mesh network.The MAC frame includes a field comprising an IMP address and an EMPaddress. When the EMP, (or optionally an intermediate mesh point),receives a data packet successfully, the EMP or the intermediate meshpoint sends an ACK to the IMP or preceding mesh point.

BRIEF DESCRIPTION OF THE DRAWINGS

A more detailed understanding of the invention may be had from thefollowing description of a preferred embodiment, given by way of exampleand to be understood in conjunction with the accompanying drawingwherein:

FIG. 1 is a diagram of a mesh WLAN in which the present invention isimplemented;

FIG. 2 is a diagram of a prior art MAC frame;

FIG. 3 is a signaling diagram for transmission of data andacknowledgement between an IMP, an EMP and intervening mesh points inaccordance with the present invention;

FIG. 4 is a diagram of a mesh MAC frame in accordance with the presentinvention; and

FIG. 5 is a flow diagram of a process for sending an ACK to the IMP inaccordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereafter, the terminology “station” (STA) includes but is not limitedto a user equipment, a wireless transmit/receive unit (WTRU), a fixed ormobile subscriber unit, a pager, or any other type of device capable ofoperating in a wireless environment. When referred to hereafter, theterminology “mesh point” includes but is not limited to a Node-B, a basestation, a site controller, an access point or any other type ofinterfacing device in a wireless environment.

The present invention is applicable to any wireless mesh networksincluding, but not limited to, IEEE 802.11, IEEE 802.11s, IEEE 802.15,IEEE 802.15.5.

FIG. 1 is a diagram of an exemplary mesh WLAN 100 comprising eight (8)mesh points 104 ₁-104 ₈. In this example, mesh point 104 ₄ is an IMP forthe STA 102 and mesh point 104 ₂ is an EMP for the data sent by the STA102.

Data sent by the STA 102 is routed from one mesh point 104 ₄ to anothermesh point 104 ₂ through the intermediate mesh points in the mesh WLAN100 for the Internet access. Multiple data paths can be establishedwithin the mesh WLAN 100. As an example, two different data paths fromthe IMP mesh point 104 ₄ to the EMP mesh point 104 ₂ are illustrated bythe solid lines designated “A” and “B” in FIG. 1.

As aforementioned with reference to FIG. 2, a drawback with the priorart 802.11 MAC frame format is that the IMP address is not included inthe MAC frame in a multi-hop transmission. The present invention solvesthis problem by including the IMP address in the MAC frame 400.Referring to FIG. 4, a diagram of a mesh MAC frame 200 in accordancewith the present invention is shown. The MAC frame 200 includes a MACheader 204, a frame body 212 and a frame check sequence (FCS) field 214.This aspect of the MAC frame format is same to the one in prior art,which guarantees backward compatibility. The MAC header 204 includes aframe control, a duration/ID, address 1, address 2, address 3, asequence control and address 4. These elements are well known to thoseof skill in the art.

In accordance with the present invention, however, the MAC header 204further includes a mesh control field 202. The mesh control field 202comprises an IMP address field 206 and an EMP address field 208. Thereceiving mesh point recognizes the IMP 104 ₄ and the EMP 104 ₂ with themesh control field 202 and may send an ACK to the IMP 104 ₄ or otherintermediate mesh point in accordance with the IMP address field 206. Itshould be noted that the MAC frame format in FIG. 4 is provided as anexample and the mesh control field 202 may be included in any locationin the MAC frame 200 and the length of the IMP and EMP address fieldsmay vary.

A routing function is available in each mesh point, which allows themesh point, based on the EMP address included in the mesh control field202, to know which path used to route the data. When the IMP 104 ₄receives an ACK, the IMP 104 ₄ can discard the related data in itsqueue. If the IMP 104 ₄ receives a non-acknowledgement (NACK), the IMP104 ₄ re-transmits the data. To avoid any buffer overflow, the IMP 104 ₄should discard the data from its queue after a certain amount of time(time-out) if the IMP 104 ₄ does not receive ACK nor NACK from the EMP104 ₂.

FIG. 3 is a signaling diagram for transmission along data path “B” of adata packet and an ACK between an IMP (in this example mesh point 104₄), an EMP (in this example mesh point 104 ₂) and intermediate meshpoints 104 ₇, 104 ₈, 104 ₆, 104 ₃, (not all of which are shown in FIG. 3for convenience), in accordance with the present invention. The datapacket is forwarded from the IMP 104 ₄ to the EMP 104 ₂ through theintermediate mesh points 104 ₇, 104 ₈, 104 ₆, 104 ₃. As will beexplained in detail hereinafter, the MAC frame 200 contains both IMP 104₄ and EMP 104 ₂ addresses in the IMP address field 206 and the EMPaddress field 208. When the intermediate mesh points 104 ₇, 104 ₈, 104₆, 104 ₃ and the EMP 104 ₂ receive a data packet successfully, theintermediate mesh points 104 ₇, 104 ₈, 104 ₆, 104 ₃ and the EMP 104 ₂send an ACK to either the preceding intermediate mesh point or the IMP104 ₄. It should be noted that FIG. 3 is an example and zero or anynumber of intermediate mesh points may exist between the IMP 104 ₄ andthe EMP 104 ₂. Additionally, the intermediate mesh points used to sendthe ACK may be same mesh points via which the data packet is forwardedor may be different mesh points.

The acknowledgement mechanism of the present invention supports bothsingle and multiple-hop data delivery over a mesh WLAN. Theacknowledgement mechanism operates in four modes: 1) EMP-to-IMP dataacknowledgement for more reliable data transfer, (e.g., FTP, HTTP); 2)single-hop data acknowledgement for reliable data transfer; 3) combinedEMP-to-IMP and single-hop data acknowledgement for very-reliable datatransfer, (e.g., signaling); and 4) no acknowledgement forhigh-throughput, packet-loss resilient, delay sensitive data transfer,(e.g., video/audio streaming).

In the first mode, (EMP-to-IMP acknowledgement), the acknowledgement isdone through all the paths. Whenever the EMP receives a packet sent bythe IMP, the EMP sends back an ACK to the originator using the IMPaddress included in the received packet.

In the second mode, (single hop acknowledgement), the acknowledgement isdone at every hop between the transmitting mesh point and the nextimmediate receiving mesh point.

The third mode, (combined EMP-to-IMP acknowledgement and single hopacknowledgement), combines the first mode and the second mode.

In the fourth mode, no acknowledgement is required between the IMP andthe EMP. Although this impacts the reliability of the data delivery, itreduces the delay in transmission.

A new frame subtype for the frame subtype information element in theframe control field 210 (shown in FIG. 4) is also defined for indicatingthat the MAC frame 200 includes the IMP address field 206 and the EMPaddress field 208. The frame control field 210 may also inform whichacknowledgement mode among the four modes stated above is to be used forthis data packet.

For the first and third mode among the four modes stated above, the MACframe format allows for an EMP-to-IMP ACK to be transmitted throughanother path different from the one used for transmission of the datapacket. To reduce the delay of transmission, the sender does not need towait for the ACK to be received before sending the next frame, (i.e.,sending and acknowledging can be asynchronous). In this case the bulkACK can be used to reduce traffic on the network. An ACK can also besent purposely via different paths depending on the traffic level inorder to reduce contention of ACKs with data. This mechanism could beused for delay sensitive and error tolerant applications such as voiceapplication.

FIG. 5 is a flow diagram of a process 300 for sending an ACK to the IMPin accordance with the present invention. A MAC frame is generated byattaching a MAC header to a data packet (step 302). The MAC headerincludes fields for an IMP address and an EMP address. The MAC frame isforwarded to the EMP either directly or via one or more intermediatemesh points (step 304). The intermediate mesh point, if there is any,and the EMP sends an ACK for successful reception of the data packet tothe IMP (step 306).

Although the features and elements of the present invention aredescribed in the preferred embodiments in particular combinations, eachfeature or element can be used alone without the other features andelements of the preferred embodiments or in various combinations with orwithout other features and elements of the present invention.

What is claimed is:
 1. In a mesh wireless communication systemcomprising a plurality of mesh points that are wirelessly linkedtogether such that a data packet sent by a station (STA) is received byan ingress mesh point (IMP) and forwarded to an egress mesh point (EMP)in order to provide a service by the mesh wireless communication system,a method for sending an acknowledgement (ACK) for the data packet to theIMP, comprising: generating a medium access control (MAC) frame fortransmission of a data packet, the MAC frame including a fieldcomprising an IMP address and an EMP address; forwarding the MAC frameto the EMP via zero or more intermediate mesh point; and sending an ACKfor successful reception of the data packet to the IMP, wherein a framecontrol field of the MAC frame indicates that the MAC frame contains theIMP address and the EMP address.
 2. The method of claim 1, wherein theframe control field of the MAC frame indicates an acknowledgement modeto be used for the data packet.
 3. The method of claim 1, wherein theACK is sent in one of: (1) an EMP-to-IMP data acknowledgement mode; (2)a single-hop data acknowledgement mode; or (3) a combined EMP-to-IMP andsingle-hop data acknowledgement mode.
 4. A method for routing a datapacket in a mesh network, the method comprising: receiving a data packetof a data communication that is sent towards a destination address froma source address, the data packet including control information thatcontemporaneously indicates a first address, as the source address, asecond address, as the destination address, a third address for aningress mesh point (IMP) through which data packets enter the meshnetwork and a fourth address for an egress mesh point (EMP) throughwhich data packets exit the mesh network; and processing the controlinformation to determine whether the data packet includes the IMPaddress and the EMP address.
 5. The method of claim 4, furthercomprising: determining, by a station receiving the data packet, whetherthe station is the EMP for the data packet using the address of the EMPindicated by the control information.
 6. The method of claim 4, whereinthe control information indicates the first, second, third and fourthaddresses in a media access control (MAC) header.
 7. The method of claim4, wherein the control information indicates six different addresses ina media access control (MAC) header.
 8. The method of claim 4, whereinthe control information is selectable to indicate four addresses or sixaddresses in a media access control (MAC) header.
 9. The method of claim4, further comprising: on condition that the station receiving the datapacket is the EMP, sending, by the EMP, an acknowledgement destined forthe IMP indicating successful reception of the received data packet ofthe data communication.
 10. The method of claim 4, wherein the controlinformation indicates one of: (1) an EMP-to-IMP data acknowledgementmode; (2) a single-hop data acknowledgement mode; or (3) a combinedEMP-to-IMP and single-hop data acknowledgement mode.
 11. A station(STA), comprising: a receiver and a processor configured to: receive adata packet of a data communication that is sent towards a destinationaddress from a source address, the data packet including controlinformation that contemporaneously indicates a first address, as thesource address, a second address, as the destination address, a thirdaddress for an ingress mesh point (IMP) through which data packets enterthe mesh network and a fourth address for an egress mesh point (EMP)through which data packets exit the mesh network; and process thecontrol information to determine whether the data packet includes theIMP address and the EMP address.
 12. The STA of claim 11, wherein theprocessor is configured to: determine whether the STA is the EMP for thedata packet using the address of the EMP indicated by the controlinformation; and on condition that the STA is the EMP, send anacknowledgement destined for the IMP indicating successful reception ofthe received data packet of the data communication.
 13. The STA of claim11, wherein the STA is configured to determine a mode of acknowledgmentfor the STA based on the control information of the data communicationindicating one of: (1) an EMP-to-IMP data acknowledgement mode; (2) asingle-hop data acknowledgement mode; or (3) a combined EMP-to-IMP andsingle-hop data acknowledgement mode.
 14. The STA of claim 1, whereinthe control information indicates the first, second, third and fourthaddresses in a media access control (MAC) header.
 15. The STA claim 11,wherein the control information indicates six different addresses in amedia access control (MAC) header.
 16. The STA of claim 11, wherein thecontrol information is selectable to indicate four addresses or sixaddresses in a media access control (MAC) header.